JPS6341491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for fixing the geographic reference of vehicles traveling within a pipeline.

It is now well known to inspect natural gas transmission pipelines for defects such as cracks and corrosion pits by sending so-called "intelligent pits" into the pipeline. Since the intelligent pit is propelled through the pipeline by gas pressure, it is possible to carry out inspections without stopping the gas supply.
The pit has built-in magnetic flux generation means for establishing a magnetic field within the pipeline, and the magnetic flux sensing coil built into the pit can detect cracks, pits, etc. that cause irregularities in the pipeline magnetic flux. Detect irregularities in pipeline walls. Instead of or in addition to generating magnetic flux, the pig may be incorporated with means for generating ultrasonic signals that are transmitted into and reflected from the wall. An ultrasonic sensor, also incorporated within the pig, detects irregular reflected signals that reflect from irregularities such as defects in the pipeline wall. The signals detected by the magnetic flux sensor or ultrasonic sensor can be recorded on tape, processed and analyzed to determine the type and extent of the defect, so that the relevant defect section of the pipeline can be repaired or can be exchanged.

Clearly, there is a need to match the defect signal with the precise location of the defect in the pipeline, in other words to fix the geographic reference or line marker of the defect. There is also a need for such systems to enable such alignment without exposing the outer walls of the pipeline.

The normal progress of the pig through the pipe is measured by a ranging wheel attached to the pig.
Although it is possible to fix the criterion for defects also by the distances measured by these rings,
The rings may slip, and over long distances their absolute measurements may not be accurate enough to accurately fix defects. Tee or other devices may be used as intermediate references in the pipeline, but in areas where these are lacking this is not possible.

It is therefore an object of the present invention to avoid the above-mentioned defects and to fix the geographical reference of the vehicle as it travels through the pipeline, eliminating the need to expose the outer walls of the pipeline. be.

According to one aspect of the invention, a method is provided for fixing the geographic reference of a vehicle traveling within a pipeline, the method detecting the presence of a vehicle within the pipeline at a selected point outside the pipeline. The process then consists of the steps of transmitting a signal from a selected reference point outside the pipeline upon detection of a vehicle, and sensing and recording this signal inside the vehicle.

Preferably, this signal is continuous, but suitably it is only transmitted for a limited period of time.

Conveniently, this signal is transmitted as magnetic flux from an alternating current coil supplied with an alternating current of a frequency not higher than 30 Hz. The frequency of the alternating current is desirably lower than 16Hz, and preferably this frequency is
Set to 20Hz.

Preferably, the detected signal is configured to generate a reference pulse for recording inside the vehicle.
Processed inside the vehicle. This reference pulse is
It is appropriate that the signal be output as soon as the disappearance of the signal is detected and after the disappearance of the signal is detected.

In a preferred embodiment of the invention, the reference pulse is
The distance traveled by the vehicle after reaching the transmitter matches a reference distance that is equal to or greater than half the distance traveled by the vehicle from the point at which the signal was first detected to the point at which the disappearance was detected. Then,
It is now being output.

According to another aspect of the invention, an apparatus is provided for fixing the geographic reference of a vehicle traveling within a pipeline, the apparatus detecting the presence of a vehicle within the pipeline at a selected point outside the pipeline. a detector for detecting, a transmitter for transmitting a signal from a selected reference point outside the pipeline in response to the detector, a sensor onboard the vehicle for detecting said signal, and a sensor onboard the vehicle for detecting said signal; Means is provided for recording said signal in response to the sensor.

Preferably, the transmitter is adapted to transmit a continuous signal and it is appropriate to provide means for limiting the period of transmission of this signal.

Conveniently, the transmitter includes an alternating current coil for transmitting the signal as magnetic flux.

Preferably, means are mounted on the vehicle for processing said signal, such that when said signal is detected by the sensor, it outputs a reference pulse for recording within the vehicle.

Suitably, the signal processing means outputs the reference pulse as soon as the disappearance of the signal is detected by the sensor, or after the disappearance of the signal is detected.

In a preferred embodiment, the signal processing means is arranged such that the distance traveled by the vehicle after reaching the transmitter is equal to half the distance traveled by the vehicle from the point at which the signal was first detected to the point at which extinction was detected. is adapted to output a reference pulse when it matches a reference distance greater than that.

Preferably, the sensor comprises a pair of crossed receive coils, the axes of which are perpendicular to each other.

Embodiments of the present invention will be described below by way of example with reference to the accompanying drawings.

The device includes a pig detection coil 1, a transmitter unit 2 connected to the coil 1 by a lead 3, a common transmitter output alternating current coil 4 connected to the transmitter unit 2 by a lead 5, and a pipeline. It is equipped with an intelligent pig 6 that can be pushed along the pipeline 7 by the pressure of the gas flowing inside it. The pick 6 includes sensor coils 8a and 8b for detecting magnetic flux signals (indicated by magnetic lines of force 9) generated by the output coil 4.
and a signal reception and processing system housed in the front part 10 of the pig 6 together with a tape recorder 11.

The pitug 6, apart from the sensor coil 8 and the signal processing system, is of conventional design, inter alia a conventional magnetic flux generator and sensor (not shown).
It also includes a resilient hoop 12 housing an ultrasound transducer in contact with the pipeline.

The pig detection coil 1 is an air-core coil, and is disposed on the ground directly above the pipe, with its axis parallel to the direction of the pipe, and upstream of the transmitting output coil 4.

In summary, the method of the present invention
It involves generating a signal in the detection coil 1 by the relative movement of the upper magnets. This signal is transmitted via lead 3 to transmitter unit 2, thereby causing transmitter unit 2 to switch on. Transmitter unit 2 energizes output coil 4 via lead 5 to transmit a magnetic flux signal for a limited period of time, for example 17 seconds, during which pig 6 passes under coil 4. The output coil 4 generates a low frequency magnetic field, a part of which enters the pipeline 7 over a short distance on either side of the coil 4. The incoming magnetic flux is detected by a sensor coil 8 attached to the front of the pig 6, and is processed by a signal receiving and processing means (described later) in the pig 6, so that the pig 6 moves directly under the coil 4. A final reference output or reference pulse is generated that indicates the position or "line marker" to be passed.

In Figure 2, the signal generated in the pig detection coil 1 is transmitted to the transmitter unit, first at 10Hz.
is filtered by a low pass filter 21 having a cutoff frequency of , and then compared with a preset threshold value in a comparator 22. When the threshold value is exceeded, the oscillator 23 is activated by the monostable means 24 for 17 seconds. Before the threshold is exceeded, a lamp 25a on the transmitter is illuminated to indicate that the transmitter unit is "waiting" for a signal.
When the monostable means 24 returns to a stable state after 17 seconds, another lamp 25b is turned on and the lamp 25a is turned off.

The oscillator 23 is crystal controlled and oscillates at a frequency of 3.2678MHz. This frequency is divided by a ²¹⁴ frequency divider built into oscillator 23, resulting in an output frequency of 200 Hz which is applied to the clock input of decade counter 26. Daycade counter 26
Of the 10 sequential outputs, the first and sixth outputs are not used. Outputs 26(2), 26(3), 26(4) and 26(5)
forms the input to the OR gate 27, while the output 2
6(7), 26(8), 26(9) and 26(10) are OR gate 2
8. When energized by sequential inputs, OR gate 27 turns on arms C and D of an inverter (indicated generally at 29) and output coil 4 connected to this inverter 29 as shown Current flows in the positive direction. Also, when activated by sequential input, OR gate 2
8 turns on the arms A and B of the inverter 29 to cause a negative current to flow through the output coil 4. As shown, the current flowing through the output coil 4 also flows through the relay coil 30, thereby energizing another lamp 25c. This lamp 25c thereby indicates that the oscillator 23 is activated. When the monostable means 24 returns to a stable state and the lamp 25b is turned on, the lamp 25c is turned off. lamp 2
5c can be colored differently for easy identification. The alternating current generated in the output coil 4 in this way causes the coil 4 to generate a magnetic field as shown in FIG.

See Figure 3. The magnetic signal generated by the output coil 4 is transmitted to a pair of sensor coils 8a and 8.
b. As shown in FIG. 3, each sensor coil 8a and 8b is provided with an analog signal processing channel, and each channel is identical. The signals from each sensor coil 8a and 8b are buffered and amplified by buffers/amplifiers 40a and 40b and then filtered by filters 41a and 41b. Filters 41a and 41b
is a bandpass filter, the low cutoff frequency is 16Hz,
The high cutoff frequency is 25Hz. The out-of-band signal rejection characteristics of these filters are -24 dB/octave above and below the cutoff frequency.

The waveformed signals are sent to comparators 42a and 42
b is compared with a preset threshold. These thresholds are variable and determine the sensitivity of the receiver. A voltage above this threshold produces a digital high signal, and a voltage below the threshold produces a digital low signal. As a result, a 20Hz square wave pulse train suitable for digital processing is obtained.

Please refer to FIG. Although not shown, the pig 6 is equipped with a distance transducer, such as a pulse tachometer, which is continuously activated while the pig 6 is moving along the pipeline 7 to generate distance measurement pulses. The output from this transducer is conditioned and provided as a 768 pulses per million (ppm) direct digital input to the first channel of the digital signal processing portion of the receiver system shown in FIG. The signal is buffered by buffer 50 and then used as the clock input to counter 51. Two outputs are taken from this counter 51. One is an output 52a obtained by dividing the frequency of the distance signal by two, and the other is an output 52b obtained by dividing the frequency by four, so that the output signals are 384 ppm and 192 ppm, respectively. These outputs are the rangefinder or odometer rate selection 5
This becomes the input to 3.

On the other hand, comparators 42a and 42b (Fig. 3)
The square wave output signal from the OR gate 55 in FIG.
is applied as input signals 54a and 54b to activate the monostable means 56 (for 82 milliseconds) so that the output of the monostable means 56 will be high while the received signal (in the form of a square wave pulse) is applied. The output of the monostable means 56 has three functions: That is, (a) set the output of odometer rate selection 53 to 384ppm.
(b) Activating received signal counters 57a and 57b; and (c) activating counters 58 and 59 until a reference pulse is generated.

When activated, counter 58 counts and divides the odometer pulses down to 3 ppm. These divided pulses clock a counter 59 provided with outputs 59a, 59b, 59c and 59d having 2 ¹ , 2 ² , 2 ³ and 2 ⁴ outputs. These outputs become the signal B inputs to digital word comparator 60. The "jam" A inputs from match distance input 61 are set to provide the selected match delay distance in meters and are also inputs to word comparator 60. Once this distance has elapsed (ie, once A input = B input and 7680 odometer pulses have been received), one pulse will be generated at the A=B output of word comparator 60. This pulse triggers the monostable means 62 to generate an output reference pulse to be recorded on the tape of a tape recorder connected to the output 63. This output reference pulse is also used to reset the receiver by OR gate 64 on line 63a.

To prevent spurious pulses from being recorded, a 100 ms pulse is applied to the monostable means 62 through line 63b to the OR gate 64 and to the output of the OR gate 55 upon switch-on ( (not shown). Additionally, line marker signals 54a and 54b are applied to the clock inputs of octal counters 57a and 57b, respectively. When either of these counters counts eight pulses, a high logic signal is generated at the output of OR gate 65. This high logic signal is applied to latch 66, thereby activating counters 58 and 59 via OR gate 67, which is also activated by the signal from monostable means 56. The high logic signal remains present until a reset pulse is applied to input line 63a of OR gate 64 to clear latch 66.

Please refer to FIGS. 5 and 6. Sensor coil 8
a and 8b are adapted to be attached to the front part of the pig 6, and are crossed at 90 degrees to each other. These coils 8a, 8b are connected to the output coil 4.
When the generated magnetic flux turns yellow, an output voltage is generated.
The amount of magnetic flux coupled to either sensor coil 8 depends on the angle between the coil 8 and the output coil 4. The angle of the sensor coil 8 is the same as that of the pipeline 7.
The rotation of the pig 6 as it passes through the coils 8 also causes an orientation such that no magnetic flux is coupled to one of the coils 8. These coils 8a, 8b are crossed so that no matter how the pig 6 is oriented, a signal can be received by either coil. Having the coils crossed in this manner is advantageous because they are perpendicular to the lines of magnetic force generated by the magnetic vehicle and therefore pick up less magnetic noise.

Please refer to FIG. The transmitter unit 2 is activated by a signal from the pig detection coil 1 (FIG. 1) before the pig 6 reaches the output coil 4, causing the output coil 4 to generate an alternating signal. The sensor coil 8 on the pig 6 detects this signal, and the shape of the detected signal is as shown at 70 in FIG.
That is, the detected signal is symmetrical about the position of the output coil 4, increases as the pig 6 approaches the coil 4, becomes maximum when the pig 6 passes directly under the coil 4, and increases as the pig 6 approaches the coil 4. It decreases as you get further away. Of course, the sensed signal 70 is processed by the processing system described in FIG. 3 and appears as a threshold-adjusted square wave pulse train 71 at the outputs of comparators 42a and 42b in FIG. Therefore, it will be understood that the center of this pulse train 71 provides the exact position of the line marker output coil 4. However, it is natural that the end of the pulse train 71 is obtained after passing this center position. Nevertheless, calculation of the center of pulse train 71 is made possible by the following method performed within the signal processing system of FIG.

In FIG. 7, it is assumed that the pig 6 approaches the pipeline 7 from the left side, and the operation when it enters the output coil area is as follows.

(i) When the detected line marker signal 70 exceeds the threshold at X1 (Figure 7), the 768 ppm ranging pulse from the distance transducer is counted by the counter 51 in Figure 4 and The signal is rotated and output to the output 52b.

(ii) When the detected line marker signal 70 falls below the threshold value at
After being further divided by , the signal is stored in word comparator 60 . This value corresponds to half the threshold distance, ie B/2.

(iii) Counting of distance measurement pulses is continued by the counter 51 in area A, but this time the frequency is divided by two. These pulses are further divided in the counter 59 and then sent to the word comparator.
At 60, it is added to B/2 and stored.

(iv) The pulse sum accumulated after each ranging pulse is compared to D (preset match distance) stored in match distance input 61.

(v) When the sum equals D, a reference pulse or line marker pulse is output. This output occurs when the pig 6 passes a certain preset distance D past the coil 4.

The fixed distance must be large enough to allow the sensed line marker signal to fall below a threshold before an output occurs. In other words, the distance A should be at least equal to 0, since if it is smaller than 0 it will introduce a distance error.

The accuracy of this method of line markers is absolute and does not depend on the accuracy of activation of the transmitter unit or vary with the speed of the pig.

The actual line marker pulse will be generated at a certain distance (eg 10 meters) after the pig 6 has passed through the transmitter output coil 4.

The frequency of the magnetic flux signal is 20 Hz, which is low enough not to generate significant and unwanted eddy currents.

The pig detector described above detects magnetic type pigs which create a direct magnetic disturbance in the detector, thereby generating a signal in the receiver coil of the detector unit. When this signal exceeds a preset threshold, the transmitter unit switches on.

However, it is clear that by appropriate selection of the detector it is also possible to detect "non-magnetic" pigs. Even non-magnetic pigs cause disturbances in the Earth's magnetic field, which can be detected by using a more sensitive magnetometer instead of a detector with a simple input coil. However, the magnetometer signal is also compared to a preset threshold and used to switch on the transmitter unit.

[Brief explanation of drawings]

1 is a schematic diagram of the device according to the invention, FIG. 2 is a block diagram of the components of the transmitter, and FIG. 3 is a block diagram of the analog signal processing portion of the transmitter system on board the pig. Figure 4 is a block diagram of the digital signal processing section of the transmitter system mounted on the pig, and Figure 5 is a perspective view of the two intersecting receiving coils mounted on the pig, seen from the rear. 6 is a rear view of the coil shown in FIG. 5, and FIG. 7 is a processing of the sensed signal to generate a reference pulse at a known distance from the location of the transmitter output coil. It is an explanatory diagram of a method. 1... Pig detection coil, 2... Transmitter unit,
3, 5...Lead, 4...Transmitter output (AC) coil, 6...Intelligent pig, 7...Pipeline, 8...Sensor coil, 9...Magnetic flux signal (magnetic field line), 10...Pig front part, 11...Tape recorder,
12...Elastic ring, 21...Low pass filter, 2
2, 42... Comparator, 23... Oscillator, 24,
56, 62... Monostable means, 25... Lamp, 26...
Daycade counter, 27, 28, 55, 64,
65, 67...OR gate, 29...inverter, 3
0...Relay coil, 40...Buffer/amplifier, 4
1...Band pass filter, 50...Buffer, 51,
58, 59...Counter, 52...Counter output, 5
3... Odometer rate selection, 54... Output of comparator 42, 57... Received signal counter, 60... Digital word comparator, 61... Match distance input, 63... Reference pulse output, 66... Latch, 70
...Sensor coil output signal, 71...Square wave pulse train.

Claims (1)

[Scope of Claims] 1. Detecting the presence of a vehicle within the pipeline at a selected point outside the pipeline, transmitting a signal from the selected reference point outside the pipeline upon detection of the vehicle, and transmitting a signal within the pipeline at a selected point outside the pipeline. A method for fixing the geographical reference of a vehicle traveling in a pipeline, characterized in that the method comprises the step of detecting and recording this signal at. 2. A method according to claim 1, characterized in that said signal is continuous. 3. Method according to claim 2, characterized in that said signal is transmitted only for a limited period of time. 4. A method according to claim 1 or 2, characterized in that the signal is transmitted as a magnetic flux from an alternating current coil transmitter supplied with an alternating current of a frequency not higher than 30 Hz. 5. A method according to claim 3, characterized in that the frequency of said alternating current is not lower than 16 Hz. 6. The method according to claim 4 or 5, characterized in that the frequency of the alternating current is 20 Hz. 7. Claim 2, characterized in that the detected signal is processed inside the vehicle to generate a reference pulse for recording inside the vehicle.
7. The method according to any one of 6. 8. A method according to claim 7, characterized in that said reference pulse is outputted as soon as said signal detects extinction or after said extinction is detected. 9. Said reference pulse is equal to or greater than the distance traveled by the vehicle after reaching the transmitter and half the distance traveled by the vehicle from the point at which the signal was first detected to the point at which extinction was detected. 9. The method according to claim 8, wherein the method is output when the reference distance matches the reference distance.